Interior poly vapor barrier?
I’m renovating a cape built in 1955 in Falmouth, Maine zone 6A. I have created two new stacked bathrooms. Both have one 8′ wall which is the exterior wall. The original house is framed with 2×4 wood studs and has 3/4″ T&G wood sheathing and wood shingle siding. I removed the old interior plaster finish and framed an additional 2×4 wood stud wall just inside the old. I have installed a layer of 3 1/2″ ROXUL with the old studs and a second 3 1/2″ layer of ROXUL within the second wall studs.
The two layers are pushed tight to each other. There is a new 3′ x 4′ PARADIGM double-hung window in the center of this wall. The interior finish will be 1/2″ HARDY tile backer board for the first 3′-6″ then 4′ high painted 1/2″ gypsum wall board up to the ceiling. The ceiling is the old 3/8″ plaster on 1/2″ gypsum backer board.
My question is: should I install a 6 mil poly vapor barrier to the inside face of new wood studs before applying the finished boards?
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